Hi Sabenza,

The onroad casing should sit over the head of the engine and rest on the pipe / carb inlet so covers a small part of the crank case. As this is a universal casing for onroad engines it will differ slightly between engines where it sits but this doesn’t make a noticeable difference in the operation. It will rest in place on its own and won’t require you to push or hold it in place.

I think once you try the unit it will all become clear. Your unit should come with instructions, if for some reason it doesnt have any let me know and I can email you an electronic version.

Hope that helps